Conventionally a corrective tool mounted on a seat surface to correct posture and the like is known of. The corrective tool includes an approximately halved cylindrical convex portion. The corrective tool is mounted on the seat surface to have a positional relationship in which the longitudinal direction of the convex portion is parallel to the right-left direction of the human body. The human body then sits on the seat surface and the corrective tool (refer to Patent Document 1).
Patent Document 1: Japanese Unexamined Patent Application, Publication No. H10-313970